Avoid conflicts when merging branches with mixed normalization

Currently, merging across changes in line ending normalization is
painful since files containing CRLF will conflict with normalized files,
even if the only difference between the two versions is the line
endings.  Additionally, any "real" merge conflicts that exist are
obscured because every line in the file has a conflict.

Assume you start out with a repo that has a lot of text files with CRLF
checked in (A):

      o---C
     /     \
    A---B---D

B: Add "* text=auto" to .gitattributes and normalize all files to
   LF-only

C: Modify some of the text files

D: Try to merge C

You will get a ridiculous number of LF/CRLF conflicts when trying to
merge C into D, since the repository contents for C are "wrong" wrt the
new .gitattributes file.

Fix ll-merge so that the "base", "theirs" and "ours" stages are passed
through convert_to_worktree() and convert_to_git() before a three-way
merge.  This ensures that all three stages are normalized in the same
way, removing from consideration differences that are only due to
normalization.

This feature is optional for now since it changes a low-level mechanism
and is not necessary for the majority of users.  The "merge.renormalize"
config variable enables it.

Signed-off-by: Eyvind Bernhardsen <eyvind.bernhardsen@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/convert.c b/convert.c
index e41a31e480..0203be8623 100644
--- a/convert.c
+++ b/convert.c
@@ -93,7 +93,8 @@ static int is_binary(unsigned long size, struct text_stat *stats)
 	return 0;
 }
 
-static enum eol determine_output_conversion(enum action action) {
+static enum eol determine_output_conversion(enum action action)
+{
 	switch (action) {
 	case CRLF_BINARY:
 		return EOL_UNSET;
@@ -693,7 +694,8 @@ static int git_path_check_ident(const char *path, struct git_attr_check *check)
 	return !!ATTR_TRUE(value);
 }
 
-enum action determine_action(enum action text_attr, enum eol eol_attr) {
+static enum action determine_action(enum action text_attr, enum eol eol_attr)
+{
 	if (text_attr == CRLF_BINARY)
 		return CRLF_BINARY;
 	if (eol_attr == EOL_LF)
@@ -773,3 +775,13 @@ int convert_to_working_tree(const char *path, const char *src, size_t len, struc
 	}
 	return ret | apply_filter(path, src, len, dst, filter);
 }
+
+int renormalize_buffer(const char *path, const char *src, size_t len, struct strbuf *dst)
+{
+	int ret = convert_to_working_tree(path, src, len, dst);
+	if (ret) {
+		src = dst->buf;
+		len = dst->len;
+	}
+	return ret | convert_to_git(path, src, len, dst, 0);
+}